Method of fracturing subterranean formations with crosslinked fluid

A method of fracturing a subterranean formation penetrated by a wellbore, comprising:

• a) pumping a viscous fracturing fluid comprising an aqueous fluid, a hydratable polymer, a crosslinking agent and proppant into the wellhead of the wellbore and through an entrance site in the wellbore into the reservoir;
• (b) propagating fractures within the formation;
• and
• (c) decreasing the apparent viscosity of the fluid distally from the entrance site during propagation of the fractures such that at least one of the following conditions prevail:
• (i) the apparent viscosity of the fracturing fluid 100 feet from the entrance site is less than 10 percent of the apparent viscosity of the fracturing fluid at the entrance site;
• (ii) the apparent viscosity of the fracturing fluid 15 minutes after introduction into the entrance site is less than 15% of the apparent viscosity of the fracturing fluid at the entrance site;
• or
• (iii) the apparent viscosity of the fracturing fluid is less than 10 cP within 15 minutes after being introduced through the entrance site.

A method of fracturing a subterranean formation penetrated by a wellbore, wherein the permeability of the subterranean formation is between from about 10 nanodarcies to about 1.0 mD, the method comprising:

• (a) forming a viscous fracturing fluid by mixing water, viscosifying polymer, crosslinking agent and proppant, wherein the viscous fracturing fluid has a viscosity between from about 10 to about 120 cP at a temperature range between from about 80° F. to about 125° F.;
• (b) pumping the viscous fracturing fluid into the wellhead of the wellbore while minimizing settling of proppant from the fluid during the pumping;
• (c) transporting the viscous fracturing fluid through an entrance site in the wellbore;
• (d) propagating fractures in the formation;
• and
• (e) decreasing the viscosity of the viscous fracturing fluid upon the fluid entering the entrance site such that at least one of the following conditions prevail:
• (i) the apparent viscosity of the fracturing fluid 100 feet from the entrance site is less than 10 percent of the apparent viscosity of the fracturing fluid at the entrance site;
• (ii) the apparent viscosity of the fracturing fluid 15 minutes after introduction into the entrance site is less than 15% of the apparent viscosity of the fracturing fluid at the entrance site;
• or
• (iii) the apparent viscosity of the fracturing fluid is less than 10 cP within 15 minutes after being introduced through the entrance site.